1. Field of the Invention
The present invention relates to a delivery pump for high pressure pumps and in particular, to the drive of delivery pumps which work according to the reciprocating-plunger principle.
2. Discussion of Background
High-pressure delivery pumps have a plunger stroke which is relatively long in relation to the plunger diameter and are therefore suitable for producing high pressures. Such high-pressure delivery pumps are used, for example, for producing the injection pressure in fuel injection systems (e.g., common rail) for internal combustion engines. A high-pressure delivery pump of the generic type is disclosed in EP-A-881 380 A1 (hereinafter "EP '380").
High-pressure delivery pumps of the generic type have a high-pressure cylinder or plunger cylinder and a cylindrical plunger movable therein in a reciprocating manner. The volume of the delivery space inside of the high-pressure cylinder is varied by the stroke movement of the plunger. During the filling stroke of the plunger, the delivery space can be connected to a supply space for a flow medium via a filling valve to fill the delivery space. The delivery space increases in swept volume with the flow medium. During a following delivery stroke with the filling valve closed, the pressure in the delivery space increases until a pressure valve opens and thereby connects the delivery space to a high-pressure space. The precise design of the high pressure pump is described in EP '380, the disclosure of which is hereby incorporated by reference so as to be expressly made the contents of the present application.
The plunger is driven by an eccentric drive. The eccentric drive includes an eccentric and said at least one relieved portion includes first and second relieved portions laterally defining said contact area, said first and second relieved portions each being provided at said outer circumference of said rolling ring. A disk-like widened portion is provided at a first end of the pre-loaded plunger. Because of the force ratios when passing through the top and bottom dead centers, the rolling ring rotates back and forth in the process and changes its direction of rotation twice during each revolution of the eccentric and eccentric shaft. This may lead to damage to the components of the eccentric drive at a high rotational speed of the eccentric shaft.